American Jack Sock, who had to change a malfunctioning pair of shoes before starting the third set Wednesday night, used the upgrade in footwear to post the biggest win of his young career. Sock, 20, upset No. 2 seed Milos Raonic of Canada, 6-3, 5-7, 7-5 to move into Thursday’s third round against his doubles partner, James Blake.

Sock, ranked 168th, won for the first time, in two matches, this season. He played only 12 matches last season.

“I had a good energy level and I was focused and ready to go,” said the hard-serving Sock, who finished with 11 aces. “I got here last Thursday so I had a good week of practice with my coach. And my body felt well.”

Sock injured his right ankle during qualifying last month in Brisbane and had only played one tour-level match, which was last weekend in San Jose. He got a key break of serve to go up 6-5 in the third when Raonic was unable to return a Sock shot that hit the tape and dropped over the net.

“I was very fortunate, but that’s tennis,” said Sock, who received a wild card into the event. “Things happen.”

As for the shoes, he said the outside of his right shoe ripped apart.

“When I moved out to the right I was falling through my shoe,” he said. “I had to play with it for three games.”

Raonic, ranked 14th, had been runner-up in Memphis the past two years.

“He was doing a few things well, he was hitting his forehand well, and I was giving away too many points,” he said. “It sort of added up. It’s unfortunate. I didn’t think this could have happened, but it did.”

Raonic had not been broken in 77 indoor service games until he was broken in the opening set Wednesday.

“I wasn’t swinging freely or hard enough in the beginning,” Raonic said. “I was fluffing the ball over the net and that allowed him to get into a rhythm.”